The effects of different prone positioning angles on cardiopulmonary function in children after congenital heart disease surgery: a randomized controlled trial

To evaluate the effects of different head-elevated prone positioning angles on oxygenation, respiratory mechanics, hemodynamics, and enteral nutrition tolerance in children after congenital heart disease（CHD）surgery, and to determine the optimal intervention angle. In this randomized controlled trial, 102 mechanically ventilated children after congenital heart disease surgery were randomly assigned to the 10°, 30°, or 45° group. 98 completed the protocol and were analyzed. All patients received standardized prone positioning for at least 12 hours per day. The primary outcome was the PaO₂/FiO₂ ratio and respiratory mechanics (lung compliance, airway resistance, and respiratory rate). Secondary outcomes included gastric residual volume, hemodynamic parameters, and complications. Repeated outcomes were analyzed using linear mixed-effects models, whereas change scores were compared using one-way ANOVA or Kruskal-Wallis tests, as appropriate. This trial was retrospectively registered at ClinicalTrials.gov (NCT07323979) on 24/12/2025 after study completion. Oxygenation improved over time in all three groups. The 10° group showed the greatest early improvement in oxygenation, the 30° group demonstrated the most favorable overall performance in lung compliance, airway resistance, and respiratory rate, and the 45° group showed the greatest reduction in gastric residual volume but more pressure-injury events were observed. Overall, the findings suggest different benefit-risk profiles across the three evaluated angles, with the 30° position representing a reasonable option when respiratory mechanics, enteral nutrition tolerance, and safety are considered together. Considering pulmonary function, enteral nutrition tolerance, and safety, the 30° head-elevated prone position may be considered a reasonable intervention angle for children after CHD surgery. In clinical practice, a 30° head-elevated prone position may offer a balanced postoperative strategy for mechanically ventilated children after congenital heart disease surgery by improving respiratory mechanics, supporting enteral feeding tolerance, and helping standardize nurse-led prone positioning practice in the CICU to support safer early postoperative recovery.